Help with routes

Switching our routes file from Rails2 to Rails3 DSl uncovered an odd situation, of my own making, but I am having some difficultly imagining how to fix it.

Basically I have a commonplace: user -> user_role (clearance) <- role type arrangement where:

User   has_many :roles, :through => :clearances   has_many :clearances

Clearance   belongs_to :role   belongs_to :user

and

Role   has_many :users, :through => :clearances   has_many :clearances

What I am trying to do is to link through new_user_role_path(@user). But I get the following error when I try:

ActionController::RoutingError: No route matches   {:action=>"new", :controller=>"user_roles"}

The thing is that when I run rake routes I see this:

new_user_role GET /users/:user_id/role/new(.:format)                       {:controller=>"user_roles", :action=>"new"}

So, I am somewhat nonplussed as to what is going on. I probably am misunderstanding something basic but from my point of view it seems that the route that is shown as missing is actually there. Is there something else I am overlooking?